Certain embodiments of the present invention relate to an ultrasound machine for displaying an image of moving structure. More particularly, certain embodiments relate to displaying displacement of moving structure such as distance moved and deformation.
Echocardiography is a branch of the ultrasound field that is currently a mixture of subjective image assessment and extraction of key quantitative parameters. Evaluation of cardiac wall function has been hampered by a lack of well-established parameters that may be used to increase the accuracy and objectivity in the assessment of, for example, coronary artery diseases. Stress echo is such an example. It has been shown that the subjective part of wall motion scoring in stress echo is highly dependent on operator training and experience. It has also been shown that inter-observer variability between echo-centers is unacceptably high due to the subjective nature of the wall motion assessment.
Much technical and clinical research has focused on the problem and has aimed at defining and validating quantitative parameters. Encouraging clinical validation studies have been reported, which indicate a set of new potential parameters that may be used to increase objectivity and accuracy in the diagnosis of, for instance, coronary artery diseases. Many of the new parameters have been difficult or impossible to assess directly by visual inspection of the ultrasound images generated in real-time. The quantification has required a post-processing step with tedious, manual analysis to extract the necessary parameters.
Academic work has been done for validation of peak, mean systolic velocities as an indicator of, for example, ischemia in stress echo. A related parameter to peak systolic motion is displacement calculated as a velocity time integral during systole. Similar related displacement parameters may be defined for any sub-interval of the cardiac cycle. Displacement parameters derived from the time integral of velocity measurements or strain rate measurements have very low noise content compared to peak detection and are, therefore, attractive parameters to use for quantitative assessment of wall function. Therefore, it may be useful to design a mechanization that makes it easy to visually assess displacement of cardiac wall tissue in a quantitative manner.
Much of the prior art describes techniques for color mapping estimated imaging parameters such as tissue velocity and strain rate. A fixed mapping of a continuous range of color hues is typically used to indicate positive velocities or strain rates and a second fixed mapping of a continuous range of color hues is used to indicate negative velocities or strain rates. This type of color encoding makes it easy to identify reversals in velocities or strain rates. However, the tissue velocity imaging (TVI) and strain rate imaging (SRI) modes and associated color mapping schemes in the prior art are not, by themselves, well suited for visual determination of other parameters, such as displacement measured as time integrated velocities or time integrated strain rates over a portion of the cardiac cycle.
A need exists for an approach to more easily visualize tissue displacement information, such as time integrated velocity and time integrated strain rate, in a two-dimensional dimensional ultrasound image.
An embodiment of the present invention provides an ultrasound system for generating an image responsive to moving cardiac structure by displaying color characteristics representative of tissue displacement.
An apparatus is provided in an ultrasound machine for generating an image responsive to moving structure within a region of interest of a subject and displaying a color characteristic representing displacement of the moving structure. In such an environment apparatus displaying the color characteristic comprises a front-end arranged to transmit ultrasound waves into a structure and then to generate received signals in response to ultrasound waves backscattered from the structure in the region of interest over a time period. A processor is responsive to the received signals to generate a parameter value representing displacement of the moving structure during the time period and is responsive to the parameter value to generate a color characteristic signal representative of the displacement. A display is arranged to display a color representation of the displacement in response to the color characteristic signal.
A method embodiment is also provided in an ultrasound machine for generating an image responsive to moving structure within a region of interest of a subject and for displaying a color characteristic representing displacement of the moving structure. In such an environment, the method for displaying the color characteristic comprises transmitting ultrasound waves into the structure and generating received signals in response to ultrasound waves backscattered from the structure in the region of interest over a time period. A parameter value representing displacement of the moving structure during the time period is generated in response to the received signals. A color characteristic signal, representative of the displacement, is generated in response to the parameter value. A color representation of the moving structure is displayed in response to the color characteristic signal.
Certain embodiments of the present invention afford an approach to visualize the color display of the displacement of moving structure with a degree of convenience and accuracy previously unattainable in the prior art.